THIS INVENTION relates to polymerization. It relates in particular to a process for producing a propylene/1-pentene polymer, and to a polymer produced in such a process.
According to a first aspect of the invention, there is provided a process for producing a propylene/1-pentene polymer, which process comprises reacting propylene, as a first monomer reactant, with 1-pentene, as a second monomer reactant, in a reaction zone, in the presence of a Ziegler-Natta catalyst or catalyst system, to form the propylene/1-pentene polymer, with the reactants being in the vapour phase in the reaction zone while the reaction is in progress, and with no liquid component being present in the reaction zone while the reaction is in progress.
While the temperature in the reaction zone, ie the reaction temperature, can be in the range of 10xc2x0 C. to 130xc2x0 C., it is preferably in the range of 40 to 110xc2x0 C., still more preferably in the range of 60xc2x0 to 90xc2x0 C.
While the pressure in the reaction zone, ie the reaction pressure can be in the range of 1 to 60 kg/cm2, it is preferably in the range of 3 to 40 kg/cm2, more preferably in the range of 6 to 30 kg/cm2.
The reaction zone may be stirred while the reaction is in progress. Preferably, the stirring of the reaction zone may be effected by means of a mechanical type of stirrer. Most preferred is a stirred reaction zone which provides an upward movement of the copolymer particles which are produced therein, without sedimentation of these particles at the bottom of the reaction zone occurring to a significant degree.
The reaction of propylene and 1-pentene is exothermic, and the process may thus include, if necessary, removing at least some of the heat of reaction. The removal of the heat of reaction may be effected by providing. internal or external coolers to the reaction zone; by withdrawing a portion of the gaseous monomer reactants from the reaction zone, cooling this portion, and recycling this portion to the reaction zone in cooled or liquefied form; or the like.
The reaction will be continued for a sufficient period of time to obtain a desired degree of conversion of the monomer reactants, hereinafter also referred to as monomers for brevity. Typically, the conversion can be in the range of 1% to 99%. Thus, the reaction time may be between 10 minutes and 48 hours, preferably between 20 minutes and 200 minutes.
The Applicant has found that different methods of introducing the monomer reactants into the reaction zone, give different performances of the process. Thus, the 1-pentene may be introduced into the reaction zone in vapour phase or it can be introduced into the reaction zone at least partially in liquid phase, with the liquid phase being evaporated in the reaction zone.
In one embodiment of the invention, both the monomer reactants may be introduced into the reaction zone in the vapour phase. Thus, the monomer reactants can then be preheated prior to introducing them into the reaction zone, to ensure that they are in vapour phase.
In one version of this embodiment of the invention, the propylene and 1-pentene may be preheated separately and introduced separately into the reaction zone.
In another version of this embodiment of the invention, the propylene and 1-pentene may be preheated separately, thereafter admixed, and then introduced together, ie as an admixture, into the reaction zone.
In still another version of this embodiment of the invention, the propylene and 1-pentene may be preheated together, ie after combining them to form an admixture, and thereafter introduced together, ie as the admixture, into the reaction zone.
In another embodiment of the invention, the monomer reactant(s) may be introduced into the reaction zone partly in the vapour phase, so that part of the monomer reactant(s) are introduced into the reaction zone in liquid phase, with this part being further evaporated in the reaction zone so that the reaction is performed with both monomer reactants in the vapour phase.
In one version of this embodiment of the invention, the propylene may be introduced into the reaction zone in the vapour phase, while the 1-pentene is introduced into the reaction zone separately in the liquid phase in such an amount that it rapidly evaporates in the reaction zone so as also to be in the vapour phase.
In another version of this embodiment of the invention, a major proportion of both propylene and 1-pentene may be introduced into the reaction zone in vapour phase, while a minor proportion of each of the monomers is introduced into the reaction zone in liquid phase in such an amount that it rapidly evaporate in the reaction zone so as also to be in the vapour phase.
It will thus be appreciated that while a portion of at least one of the monomer reactants can be introduced into the reaction zone in the liquid phase, any liquid monomer reactant that enters the reaction zone is rapidly vaporized so that all monomer reactants are in the vapour phase when they partake in the polymerization reaction. Additionally, the process is characterized thereby that no liquid component is present in the reaction zone while the reaction is in progress. By xe2x80x98liquid componentxe2x80x99 is meant any component, whether capable of reacting with the monomer reactants or not, which is in liquid form at the reaction conditions prevailing in the reaction zone and which would remain in liquid form if introduced into the reaction zone. The liquid component does thus not include the monomer reactants, which can be introduced into the reaction zone in partly liquefied form as hereinbefore described, but which vaporize rapidly on entering the reaction zone. The liquid component also does not include the resultant propylene/1-pentene polymer, which can be in liquid form at the reaction conditions prevailing in the reaction zone. The liquid component also does not include any liquids present as part of the catalyst system, such as alkyl aluminium and stereoregulators, which remain liquid in the reaction zone but are present therein in very small or negligible amounts only, typically less than 0.5% (based on the total reaction zone content). The catalyst system also may contain a carrier such as heptane, but these carriers also rapidly vaporize on entering the reaction zone.
It will be appreciated that while the propylene/1-pentene polymer will normally be a copolymer of propylene and 1-pentene only, if may also, if desired, contain minor proportions of other monomers, which will then also be introduced into the reaction zone as monomer reactants and will then also be in the vapour phase while the reaction is in progress.
The 1-pentene may be that obtained by an appropriate process. Thus, for example, it may be that obtained from a Fischer-Tropsch synthesis reaction, typically that obtained from the SASOL (trade mark) Fischer-Tropsch synthesis reaction process.
Any Ziegler-Natta catalyst or catalyst system for propylene polymerization in vapour phase can, at least in principle, be used. However, a catalyst system comprising a titanium based Ziegler-Natta catalyst and, as a cocatalyst, an organo-aluminium compound, is preferred.
Typical titanium components of the Ziegler-Natta catalyst are titanium trichloride and titanium tetrachloride, which may be carried on a support. Catalyst support and activation can be effected in known fashion. For the preparation of the titanium catalyst, halides or alcoholates of trivalent or tetravalent titanium can be used. In addition to the trivalent and tetravalent titanium compounds and the support or carrier, the catalyst can also contain electron donor compounds, eg mono or polyfunctional carboxyl acids, carboxyl anhydrides and esters, ketones, ethers, alcohols, lactones, or organic phosphorous or silicon organic compounds.
An example of a preferred titanium-based Ziegler-Natta catalyst is TiCl3.1/3AlCl3.1/3(n-propyl benzoate [NPB]), which is commercially available.
However, the Applicant has also surprisingly found that when particular methods of catalyst preparation are used, process advantages in each particular embodiment or aspect of the invention may be obtained, and consequently the range of propylene/1-pentene polymers produced can be extended considerably.
Thus, the titanium-based Ziegler-Natta catalyst may be that obtained by contacting an activated magnesium chloride with titanium tetrachloride in the presence of a suitable electron donor.
Thus, the activated magnesium chloride is the support of the catalyst. The magnesium chloride may be used in the form of anhydrous magnesium chloride, providing that the anhydrization thereof is effected in such a manner that no anhydrization agent remains in the anhydrized magnesium chloride which is then further used to prepare the catalyst. In another embodiment of the catalyst preparation, the magnesium chloride may, however, have a water content between 0.02 mole of water/1 mole of magnesium chloride and 2 mole of water per 1 mole of magnesium chloride. Most preferably, the water content of magnesium chloride is in one particular case, 1.5% and, in a second particular case, 5%.
The anhydrous magnesium chloride is preferably activated prior to contacting or loading it with the titanium tetrachloride.
The activation of the anhydrous magnesium chloride may be performed under inert conditions, ie in a substantially oxygen and water free atmosphere and in the absence or in the presence of an inert saturated hydrocarbon liquid. Preferred inert saturated hydrocarbon liquids are aliphatic or cyclo-aliphatic liquid hydrocarbons, and the most preferred are hexane and heptane.
The magnesium chloride or support activation may be performed in two steps (a1) and (a2).
In step (a1), an ether may be added under inert conditions to a suspension of the magnesium chloride in the inert hydrocarbon liquid or to a powder form of magnesium chloride. The ether may be selected from linear ethers having a total number of carbon atoms between 8 and 16. The most preferred ethers are: di-butyl ether and di-pentyl ether. The molar ratio of the anhydrous magnesium chloride to the ether may be between 0.3:1 and 3:1, with the preferred molar ratio being 1:1 to 2.5:1. The resultant mixture or suspension may be stirred for a period of 10 minutes to 24 hours at room temperature. The preferred stirring time is 1 to 12 hours. The temperature for preparing the partially activated magnesium chloride may be 40xc2x0 C. to 140xc2x0 C. A partially activated magnesium chloride is thus obtained.
In the second step (a2) an alkyl aluminium compound may be added, preferably in dropwise fashion, to the partially activated magnesium chloride. Typical alkyl aluminium compounds which can be used are those expressed by the formula AlRmX3xe2x88x92m wherein R is an alkyl radical or radical component of 1 to 10 carbon atoms, X is a halogen atom, and m is a number such that 0 less than mxe2x89xa63. It was surprisingly found that in a particular copolymerization of propylene with 1-pentene, two particular cases of the alkyl aluminium can lead to the formation of two particular families of catalyst which, when used in the copolymerization of propylene with 1-pentene have different behaviours. Thus, in one version, the alkyl aluminium is completely free of chlorine while in the other version, it contains chlorine. Specific examples of suitable alkyl aluminium compounds of the first version which can be used are: tri-butyl aluminium, tri-isobutyl aluminium, tri-hexyl aluminium and tri-octyl aluminium. Preferred organo-aluminium compounds are tripropyl aluminium and tri-ethyl aluminium. A preferred example of the second version or class is diethylaluminium chloride. The molar ratio of the alkyl aluminium compound to the anhydrous magnesium chloride may be between 1:1 and 25:1. The preferred molar ratio of the alkyl aluminium compound to the anhydrous magnesium chloride is 4:1 to 5:1. The amount of the aluminium alkyl added to the partially activated magnesium chloride may comply with the equation:
A greater than B+C+D
where A represents the total moles of aluminium alkyl, B represents the moles of magnesium chloride, C represents the total moles of ether, and D represents the total moles of water (as the sum of the total water present in the magnesium chloride and any traces of water in the solvent).
The activated support is further washed with a saturated hydrocarbon liquid until none of the initially introduced ether is present.
The loading of the activated magnesium chloride or support with the titanium tetrachloride may be performed in three steps (b1) (b2) and (b3).
In the first step (b1), to the support, after thorough washing thereof with hexane, may be added an electron donor under stirring. The electron donors may be selected from the class of electron donors with labile hydrogen and from the class of electron donors without labile hydrogen. Preferred electron donors with labile hydrogen are selected from the class of alcohols, while preferred electron donors without labile hydrogen are selected from the class of organic esters. The electron donors with or without labile hydrogen may be added separately. However, they are preferably added simultaneously, either separately in the same preparation step or as a multicomponent mixture. Each alcohol may be selected from the alcohol range having 2 to 8 carbon atoms. Each ester may be selected from the class of organic ester derived from and aromatic acid, diacid or an aromatic anhydride. The Applicant has surprisingly found that different performances of the catalyst are obtained in a particular embodiment or aspect of this invention if particular esters are used in this step of the catalyst preparation, Thus preferred esters are esters derived from benzoic acid, phthalic acid and trimellitic anhydride.
In one version of this embodiment of the invention, one ester may be used. In another version of this embodiment of the invention a mixture of esters may be used. In yet another version of this embodiment of the invention, a mixture of an ester and an alcohol may be used. In a more particular case of this version of the invention, the alcohol may have the same number of carbon atoms as one or both alcohols used in the preparation of the aromatic dibasic acid ester. In an even more particular case a tricomponent mixture may be used. The three component mixture may comprise three esters, or two esters and one alcohol, or two alcohols and one ester, or three alcohols.
The molar ratio of the ester, or of a mixture thereof with another ester or with an alcohol, to the initial magnesium chloride used may be between 0.05:1 and 5:1.
The molar ratio between the two esters, or between the ester and the alcohol in a mixture of the ester with the alcohol, in a dicomponent mixture, can be 100:1 to 1:100; however, the preferred molar ratio is 1:1.
The molar ratio of the components of a tri-component mixture can vary widely, but preferably is about 1:1:1.
The stirring time may be between 1 min and 10 hours, preferably about 3 hours.
The temperature range can be between 0xc2x0 C. and the lowest boiling point of the any one of the ester or alcohols from the multicomponent mixture or the solvent used in this step of the catalyst preparation.
In the second step (b2), TiCl4 may be added to the support/alcohol mixture, the mixture or slurry stirred under reflux and finally left to cool, eg for about 24 hours. The catalyst obtained may be thoroughly washed, eg with hexane.
The molar ratio of TiCl4 employed in this step to the initial magnesium chloride may be from about 2:1 to about 20:1, preferably about 10:1.
In the third step (b3) an ester is added. The Applicant has found that there are two versions of step (b3), both leading surprisingly to catalysts with different performances:
i) The ester or ester mixture is the same ester or ester mixture used in step (b1)
ii) The ester or ester mixture are different from the ester used in step (b1)
The Applicant surprisingly found that by using more particular ways of activating the support, different and advantageous process performances can be obtained, when used in the different embodiments and aspects of this invention.
Thus, in another version of this embodiment of the invention, after the step of adding an ether to the partially anhydrized magnesium chloride as hereinbefore described, an alcohol may be added. The alcohol may be selected from the range of alcohols having between two and 8 carbon atoms. The preferred amount of alcohol added in this step may be between 0.5:1 and 2:1 of the ether added and most preferred the same as the amount as ether added. The excess solvent from the resultant solution may be removed under reduced pressure until the solution is saturated such that, when followed by slow cooling, the partially activated support will crystallize, whereafter a severe washing with a saturated hydrocarbon liquid follows.
The Applicant also surprisingly found that two very different families of catalysts may be obtained when two particular ways of further treating the support are used, and that these may lead to different and advantageous process performances when used in the different embodiments and aspects of this invention.
Thus, in one aspect of this embodiment of the invention, the support activated as hereinbefore described, is treated with an alkyl aluminium as also hereinbefore described followed by steps b1, b2 and b3 as hereinbefore described. In this case the total aluminium alkyl should comply with the following equation:
A greater than B+C+D+E
where A represents the total moles of aluminium alkyl, B represents the moles of magnesium chloride, C represents the total moles of ether, D represents the total moles of water and E represents the total moles of alcohol.
In another version of this embodiment of the invention, the support activated as hereinbefore described is not treated with the alkyl aluminium, but instead thoroughly washed with an ether before the preparation is followed by the steps b1, b2 and b3 as hereinbefore described. The ether may be the same ether as the ether used in the first step of magnesium chloride activation. However, after adding the alcohol, the excess solvent from the resultant solution may be removed under reduced pressure as hereinbefore described, until the solution is saturated, such that, when followed by slow cooling the partially activated support will crystallize. Thereafter two washing steps follow. In a first washing step, the same ether is used as that employed in the activation as hereinbefore described. In the second working step a saturated hydrocarbon is used.
The Applicant also surprisingly found that a very different family of catalysts may be obtained when a particular way of adding the titanium chloride is used, and which may lead to different and advantageous process performances when used in the different embodiments and version of this invention.
Thus, in one version of this embodiment of the invention, the order of loading the titanium is by adding the titanium to the activated support as in step b2 followed by adding the electron donor as in step b1 and followed by adding again the titanium compound as in step b2.
The cocatalyst employed in the polymerization may, as stated, be an organo aluminium compound. Typical organo-aluminium compounds which can be used are compounds expressed by the formula AlRmX3xe2x88x92m wherein R is a hydrocarbon component of 1 to 15 carbon atoms, X is a halogen atom, and m is a number represented by 0 less than mxe2x89xa63. Specific examples of suitable organo aluminium compounds which can be used are: a trialkyl aluminium, a trialkenyl aluminium, a partially halogenated alkyl aluminium, an alkyl aluminium sesquihalide, an alkyl aluminium dihalide. Preferred organo aluminium compounds are alkyl aluminium compounds, and the most preferred is triethylaluminium. The atomic ratio of aluminium to titanium in the catalyst system may be between 0.1:1 and 500:1, preferably between 1:1 and 100:1.
The Applicant has surprisingly discovered that very large ranges of propylene/1-pentene copolymers and different performances of the process in each particular embodiment are obtained when external stereoregulators are used during the copolymerization according to this invention. Any stereoregulator for propylene polymerization can, in principle, be used. However the most preferred stereoregulators are silanes and modified silanes. Examples of preferred silanes are: di-iso-propyl dimethoxy silane, diphenyl dichloro silane, methyl trimethoxy silane, dimethyl-diethoxy silane, chloro trimethyl silane and phenyl triethoxy silane.
The Applicant has also surprisingly found that different methods of further conditioning the catalyst lead to particular processes which yield different copolymers. Two particular catalyst preparation methods have been found to be most suitable for copolymerization of propylene with 1-pentene according to this invention, viz a particular prepolymerized catalyst and a particular polymer diluted catalyst.
Thus, in one embodiment the invention, a prepolymerized Ziegler-Natta catalyst or catalyst system may be used.
For the prepolymerization of the Ziegler-Natta catalyst or catalyst system, alpha olefins having a total carbon number between 2 and 20 may be used. Propylene is an example of such an alpha olefin. The inventors have surprisingly found that it is most preferable to use a mixture of propylene with 1-pentene to perform the prepolymerization of the Ziegler-Natta catalyst. It is even more preferred to use a mixture of propylene and 1-pentene in a mass proportion between 99.7:0.3 and 85:15.
Thus, in one version of this embodiment of the invention, the Ziegler-Natta catalyst may be prepolymerized with propylene.
The prepolymerization may be performed in a slurry phase comprising a solid particulate Ziegler-Natta catalyst slurried in an inert highly purified liquid hydrocarbon carrier. Linear or branched aliphatic liquid hydrocarbons can be used as the carrier liquid for the prepolymerization. The preferred carrier liquids have 6-7 carbon atoms. The most preferred carrier liquid is isohexane.
The concentration of the catalyst in the slurry may be 50-10000 mg of catalyst per 100 g of solvent. Preferably, the concentration may be 600-6000 mg of catalyst per 100 g of solvent. The most preferred concentration is 2000-4000 mg of catalyst or catalyst system per 100 g of solvent.
The Ziegler-Natta catalyst may be prepolymerized in the presence of the cocatalyst, ie the organo aluminium compound. Typical organo aluminium compounds which can be used in combination with the titanium based catalyst are, as mentioned above, compounds expressed by the formula AlRmX3xe2x88x92m wherein R is hydrogen or a hydrocarbon residue of 1-15 carbon atoms, X is a halogen atom or alkoxy group of 1-15 carbon atoms, and m is an integer represented by 0 less than mxe2x89xa63. Preferred organo aluminium compounds are then a trialkyl aluminium, an alkyl aluminium sesquihalide or an alkyl aluminium halide. The most preferred organo aluminium is triethyl aluminium.
The ratio of the Ziegler-Natta catalyst to the triethyl aluminium may be 1000 mg catalyst per 0.1 to 100 mmol triethyl aluminium; preferably 1000 mg catalyst per 1 to 10 mmol triethyl aluminium; most preferably 1000 mg catalyst per 3 to 5 mmol triethyl aluminium.
The prepolymerization may be performed in a closed vessel after thorough purging with nitrogen, by continuously supplying propylene to the vessel containing the catalyst/triethyl aluminium slurry. The amount of propylene supplied may be regulated to obtain a ratio of 1 to 300 g propylene/g catalyst, preferably 3 to 5 g propylene/g catalyst. The reaction temperature may be between 0xc2x0 C. to 80xc2x0 C., preferably room temperature.
In another version of this embodiment of the invention, the Ziegler-Natta catalyst may be prepolymerized with a mixture of propylene and 1-pentene in a mass proportion between 99.7:0.3 and 85:15, using the same prepolymerization conditions as described above for the prepolymerization with propylene.
The preferred catalyst system thus contains the prepolymerized catalyst and triethyl aluminium as cocatalyst.
In another embodiment of the invention, a polymer diluted Ziegler-Natta catalyst or catalyst system may be used.
Any polymer inactive to the catalyst may be used. An example of such a polymer is a propylene polymer. A preferred polymer is a copolymer of propylene with 1-pentene, while the most preferred polymer is a propylene/1-pentene copolymer with a 1-pentene content between 0.1% and 10% by weight.
The polymer diluted catalyst may be prepared by mixing the catalyst with the polymer in powder form. The mixing may involve mechanically stirring the catalyst and the polymer powder. Other known methods of stirring can also be used. The catalyst may be added to the polymer powder in a powder form or in a slurry form. However, the inventors have found that the best results are obtained when the polymer is added to a suspension of the catalyst, in powder form, in an inert liquid hydrocarbon, the resultant slurry mixed, and the solvent thereafter evaporated to obtain the polymer diluted catalyst in powder form.
In one version of this embodiment of the invention, the polymer diluted catalyst slurry may be directly supplied to the gas phase polymerization zone provided that the temperature in the reaction zone allow rapid vaporization of the limited amount of the carrier liquid in the polymer diluted catalyst.
A cocatalyst may be added to the polymer powder support prior to the addition of the catalyst thereto, or the co-catalyst may be added to the catalyst prior to the addition thereto of the polymer powder support. The co-catalyst employed may be an organo aluminium compound. As mentioned hereinbefore, typical organo-aluminium compounds which can be used are those compounds expressed by the formula AlRmX3xe2x88x92m wherein R is a hydrocarbon component of 1 to 15 carbon atoms, X is a halogen atom , and m is a number represented by 0 less than mxe2x89xa63. Specific examples of suitable organo aluminium compounds which can be used are: a trialkyl aluminium, a trialkenyl aluminium, a partially halogenated alkyl aluminium, an alkyl aluminium sesquihalide, and an alkyl aluminium dihalide. Preferred organo aluminium compounds are alkyl aluminium compounds, and the most preferred is triethyl aluminium. The atomic ratio of aluminium to titanium in the catalyst system may be between 0.1:1 and 10000:1, preferably between 1:1 and 5000:1.
The mixing of the polymer powder with the catalyst as hereinbefore described in the presence or absence of the cocatalyst may preferably be performed at a temperature between 10xc2x0 C. and 40xc2x0 C., more preferably at ambient temperature.
Thus, according to a second aspect of the invention, there is provided a process for producing a propylene/1-pentene polymer, which process comprises reacting propylene, as a first monomer reactant, with 1-pentene, as a second monomer reactant, in a reaction zone, in the presence of a prepolymerized or polymer diluted Ziegler-Natta catalyst or catalyst system, to form the propylene/1-pentene polymer, with the reactants being in the vapour phase in the reaction zone while the reaction is in progress, and with no liquid component being present in the reaction zone while the reaction is in progress.
The prepolymerization and polymer diluted Ziegler-Natta catalyst may be as hereinbefore described.
The Applicant has discovered that by introducing the monomers into the reaction zone in different fashions, the copolymer properties can be changed and a large variety of copolymers with different application properties can be obtained. According to this invention random propylene/1-pentene copolymers or random block propylene/1-pentene copolymer may be produced.
All the 1-pentene may be introduced into the reaction zone at the start of the reaction.
Thus, according to a third aspect of the invention, there is provided a process for producing a propylene/1-pentene polymer, which process comprises reacting, for a reaction period, propylene, as a first monomer reactant, with 1-pentene, as a second monomer reactant, in vapour phase in a reaction zone in the presence of a Ziegler-Natta catalyst or catalyst system, to form the propylene/1-pentene polymer, with all the 1-pentene being introduced into the reaction zone at the beginning of the reaction period, with the ratio of propylene to 1-pentene in the reaction zone being varied continuously over the reaction period, with all the reactants being in the vapour phase in the reaction zone while the reaction is in progress, and with no liquid component being present in the reaction zone while the reaction is in progress.
In one embodiment, the propylene may be introduced continuously into the reaction zone over the duration of the reaction at a constant pressure, with the variation in the ratio of propylene to 1-pentene being realized by the continuous decrease in the ratio of 1-pentene to propylene due to the consumption of 1-pentene during the reaction and by the different ractivities of propylene and 1-pentene under the same reaction conditions.
In another embodiment, the propylene may be introduced continuously into the reaction zone over the duration of the reaction at a constant flow rate. The variation in the rate of propylene to 1-pentene is realized by the continuous decrease in the ratio of 1-pentene to propylene due to the consumption of 1-pentene during the reaction and due to different reactivities of propylene and 1-pentene under different reaction conditions.
However, instead, the 1-pentene may be introduced intermittently into the reaction zone.
Thus, according to a fourth aspect of the invention, there is provided a process for producing a propylene/1-pentene polymer which process comprises reacting, for a reaction period, propylene as a first monomer reactant, with 1-pentene, as a second monomer reactant, in vapour phase in a reaction zone in the presence of a Ziegler-Natta catalyst or catalyst system, by introducing the 1-pentene intermittently into the reaction zone and continuously modifying the ratio of propylene to 1-pentene in the reaction zone over the reaction period, to form the propylene/1-pentene polymer, with all the reactants being in the vapour phase in the reaction zone while the reaction is in progress, and with no liquid component being present in the eaction zone while the reaction is in progress.
In one embodiment, the same amounts of the 1-pentene may be introduced intermittently into the reaction zone, with the propylene being introduced continuously into the reaction zone during the reaction, at a constant pressure or constant flow. The variation in the ratio of propylene to 1-pentene may be realized by the intermittent decrease in the ratio of 1-pentene/propylene due to the consumption of 1-pentene during the reaction between the 1-pentene additions and the different reactivities of propylene and 1-pentene under the same reaction conditions.
In another embodiment, differing amounts of the 1-pentene may be introduced intermittently into the reaction zone, with the propylene being introduced continuously into the reaction zone during the reaction, at a constant pressure or constant flow. The variation in the ratio of propylene to 1-pentene is realized by the intermittent decrease in the ratio of 1-pentene/propylene due to the consumption of 1-pentene in the reaction zone between the 1-pentene additions and this decrease being different according to the amount intermittently introduced, and also by the different reactivities of propylene and 1-pentene under the same reaction conditions.
In yet another embodiment, however, both the propylene and 1-pentene may be introduced continuously into the reaction zone.
Thus, according to a fifth aspect of the invention, there is provided a process for preparing a propylene/1-pentene polymer which process comprises reacting, for a reaction period, propylene, as a first monomer reactant, with 1-pentene, as a second monomer reactant, in vapour phase in a reaction zone in the presence of a Ziegler-Natta catalyst or catalyst system by continuously introducing both propylene and 1-pentene into the reaction zone over the reaction period, to form the propylene/1-pentene polymer, with all the reactants being in the vapour phase in the reaction zone while the reaction is in progress, and with no liquid component being present in the reaction zone while the reaction is in progress.
In one embodiment of this aspect of the invention, both the propylene and the 1-pentene may be introduced continuously into the reaction zone at a constant pressure.
In another embodiment of this aspect of the invention, both the propylene and the 1-pentene may be introduced continuously into the reaction zone at a constant flow rate.
In yet another embodiment of this aspect of the invention, both the propylene and the 1-pentene may be introduced continuously into the reaction zone at a constant pressure and at a constant flow.
The reaction mixture containing the polymer may be continuously removed from the reaction zone and supplied to a separation unit where the copolymer in powder form is separated from the unreacted monomers. The operating parameters of the separating unit are selected such that substantially no unreacted propylene and/or a pentene are liquified. Such separation units are known in the art. The unreacted monomers may be recycled to the reactor with or without complete separation.
In one particular case of this embodiment of this aspect of the invention, a limited amount of propylene and 1-pentene may be partially liquified in a cooling unit and returned to the reaction zone either preheated or in the liquid form in separate line or through a monomer feed line. The propylene/1-pentene gas mixture which is not liquified in this unit is further supplied to a separation unit for propylene and 1-pentene separation.
In another particular case of this embodiment of this aspect of the invention the whole amount of propylene/1-pentene gas mixture may further be supplied to a separation unit for propylene and 1-pentene separation. Such separation units are known in the art.
In a still further embodiment of the invention, in a first step, at least some of the propylene may be homopolymerized in the reaction zone whereafter, in a second step, the 1-pentene, or the 1-pentene and the balance of the propylene, are added to the reaction zone.
Thus, according to a sixth aspect of the invention, there is provided a process for preparing a propylene/1-pentene polymer which process comprises, in a first step, homopolymerizing propylene in a reaction zone, and thereafter, in a second step, adding 1-pentene, or propylene and 1-pentene, to the reaction zone, with both steps being effected in vapour phase in the presence of a Ziegler-Natta catalyst or catalyst system, to form the propylene/1-pentene polymer, with all the reactants being in the vapour phase in the reaction zone while the reaction is in progress, and with no liquid component being present in the reaction zone while the reaction is in progress.
In one embodiment of this aspect of the invention, an amount of propylene may first be homopolymerized in the reaction zone in the first step, with the second step comprising reacting the balance of the propylene with 1-pentene by introducing the balance of the 1-pentene at the beginning of the second step and by continuously introducing the propylene into the reaction zone under constant pressure.
In another embodiment of this aspect of the invention, an amount of propylene may first be homopolymerized in the reaction zone in the first step, with the second step comprising reacting the balance of the propylene with 1-pentene by introducing the balance of the 1-pentene at the beginning of the second step and by continuously introducing the propylene into the reaction zone under constant flow.
In yet another embodiment of this aspect of the invention, an amount of propylene may first be homopolymerized in the reaction zone in the first step, with the second step comprising reacting the balance of the propylene with 1-pentene by introducing the same amounts of the balance of the 1-pentene intermittently during the second step and by continuously introducing the propylene into the reaction zone under constant flow or constant pressure.
In a still further embodiment of this aspect of the invention, an amount of propylene may first be homopolymerized in the reaction zone in the first step, with the second step comprising reacting the balance of the propylene with 1-pentene by introducing different amounts of the balance of the 1-pentene intermittently during the second step and by continuously introducing the propylene into the reaction zone under constant flow or constant pressure.
In yet a further embodiment of this aspect of the invention, an amount of propylene may first be homopolymerized in the reaction zone in the first step, with the second step comprising reacting the balance of the propylene with 1-pentene by introducing both the balance of the propylene and the 1-pentene continuously into the reaction zone at constant pressure or constant flow.
A very large range of propylene/1-pentene copolymers can be produced in accordance with each embodiment or aspect of this invention. The invention thus extends also to polymers when produced by the process according to this invention.